Aren't you misreading Blow? To me he is saying that he believed OJ to have been incontrovertibly guilty, and he couldn't believe that other blacks would disagree if they looked at the evidence as dispassionately as he did. Therefore, the only explanation for them refusing to believe the evidence against OJ because of where it was coming from, i.e. a justice system allegedly biased against blacks. He then calls this a possible intellectual argument, but not a moral one, which I took to mean it is the kind of argument an intellectual might make in order to explain black presumption of OJ's innocence, but obviously it's not an argument that could be offered as a moral defense of OJ, since any objective appraisal of the evidence must acknowledge OJ's evident guilt.